1. Technical Field
The present invention relates to surface acoustic wave apparatuses, and more specifically, to a surface acoustic wave apparatus having a semiconductor integrated circuit and a surface acoustic wave element such as a surface acoustic wave oscillator.
2. Background Art
Generally, surface acoustic wave (hereinafter, referred to as SAW) apparatuses comprise a SAW element using a SAW which propagates along a piezoelectric element. The wavelength of the SAW is shorter than that of the electromagnetic wave and the propagation speed of the SAW is slow. Therefore, since electronic devices can now be made small using the SAW element, the SAW has been widely used in portable communication terminals such as portable telephones as well as filters, vibrators, and delaying elements. As such, it is still desirable to make the SAW apparatus small.
For example, as shown in FIG. 7, a conventional SAW apparatus has a SAW element 1 and a semiconductor integrated circuit (IC) 2 which are juxtaposed with each other, while their electrodes are wire-bonded. A SAW apparatus having the above structure has problems in that it needs to secure a sufficient mounting space (cavity) for the SAW element 1 and the IC 2 on the surface of the substrate 3, which limits the miniaturization of the SAW apparatus.
In view of the drawbacks of the conventional SAW apparatus, an apparatus as disclosed in Japanese Unexamined Patent Application Publication No. 9-162691 is suggested. The SAW apparatus disclosed in Japanese Unexamined Patent Application Publication No. 9-162691 is shown in FIG. 8. In this SAW apparatus, an IC 2 is mounted on a surface of a substrate 3 to be wire-bonded to electrodes, and a SAW element 1 is mounted above an active surface of the IC 2 with bumps 4 interposed therebetween. Because the SAW element 1 is flip-chip mounted on the active surface of the IC 2, the SAW element 1 and the IC 2 are mounted with their active surfaces facing each other.
With a SAW apparatus having the above construction, it is possible to reduce the mounting area for the substrate and consequently the size of the resulting SAW apparatus.
However, in the SAW apparatus having the afore-mentioned construction, a space is required for wire bonding (electrode portion) as well as a space for mounting the SAW element on the active surface of the IC. Therefore, since the IC must be larger than the SAW element, the miniaturization of the SAW apparatus is limited. Further, since the mounting surfaces (electrode portions) of the SAW element and the IC must correspond to each other, the shape and the size of the electrode portions thereof are also limited. Also, since the IC and the SAW element are mounted by bonding their active surfaces to each other, the heat generated during the mounting process may adversely affect the active surfaces.
Accordingly, the present invention aims to solve the aforementioned problems, and it is an object of the present invention to provide a small SAW apparatus without limiting the size and the mounting position of the semiconductor integrated circuit and SAW element, and without adversely affecting the active surfaces by the mounting process.